KR950005873B1 - Numerically controlled machine tool - Google Patents

Abstract

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Description

Machine tools

1 is a block diagram showing a configuration according to a first aspect of the present invention.

2 is a block diagram showing a configuration according to a second aspect of the present invention.

3a and 3b are front views showing a grinding machine according to a first embodiment of the present invention.

4a and 4b are front views showing a grinding machine according to a second embodiment of the present invention.

5 is a schematic explanatory diagram for explaining the positional relationship between various members in dressing.

6 is a flowchart showing the actual processing performed by the machine tool according to the first embodiment of the present invention.

7 is a flowchart showing the actual processing performed by the machine tool according to the second embodiment of the present invention.

The present invention relates to a numerically controlled machine tool such as a grinding machine. In particular, the present invention relates to a machine tool having a function of correcting a machining dimension of a workpiece and / or setting a tool length after trimming or dressing of a machining grinding tool.

Conventionally, in a machine tool equipped with a numerical control apparatus (hereinafter referred to as an NC apparatus), the machining dimension is corrected by changing or setting the tool correction amount. A tool whose setting of the tool correction amount is measured by a tool presetter or the like. If it is performed only by the dimension, the influence of deformation, thermal displacement, tool wear, etc. of the machine tool and the tool cannot be corrected. Therefore, in high precision machining, it is necessary to correct the tool compensation amount by measuring the dimension of the machined workpiece.

Conventionally, the dimension measurement of a workpiece | work was isolate | separated from a machine tool and measured outside the machine.

In the case where an automatic tool changer (hereinafter referred to as an ATC device) such as a machining center is provided, a tool having a measuring device built into the tool holder is mounted on the ATC device as one of the tools, Some instruments were mounted on the spindle to measure the dimensions of the workpiece.

However, measuring the machining dimension of the workpiece outside the machine requires a lot of working time, and there is a problem in that the skill of the operator is required to appropriately correct the amount of correction of the tool correction from the measurement result.

In the case of using the ATC device, since the tool must be changed once for the measurement of the dimensions of the workpiece, time loss occurs and the state of mounting of the processing tool on the main shaft before and after the measurement changes slightly. There was a problem that the result could not be accurately reflected in the correction value.

Machining programs in machine tools with NC devices are programmed using tool length compensation to give universality. Grinding machines require the trimming or dressing of the grinding tool used in the machining, and the measurement of the tool length and the correction of the tool compensation values are required for each trimming or dressing.

Conventionally, the tool length was measured by separating the grinding tool from the main shaft and using a tool processor or the like outside the machine. The tool length correction value was set in accordance with the tool size.

Moreover, on the machine with the grinding tool mounted on the main shaft, the tool size was measured and set so as to contact the grinding tool of the reference block whose dimensions were measured in advance. Instead of the reference block, the grinding tool was brought into contact with a touch switch provided on the fixed part, and the tool dimension was measured by automatic operation.

However, in the grinding machine of the first type, in the measurement of the tool length outside the machine, the grinding tool must be detached from the spindle once for measurement, and time loss occurs and the mounting state of the grinding tool on the spindle after measurement is subtle. There is a problem that the measurement result is not accurately reflected in the correction value.

In the grinding machine of the second type, there is a problem in that the measurement of the tool length by the reference block on the machine is performed by manual operation, which results in a loss of time and the skill required for accurate measurement.

Further, the grinding machine of the third type cannot measure the amount of change (reduction amount) of the grinding or dressing grindstone polished together with the grinding tool at the automatic opening of the tool length by a touch sensor fixed on the machine or the like.

That is, in any of the above methods, there has been a problem that the program data for trimming or dressing must be corrected for each execution of dressing or the like, resulting in a time loss.

The present invention has been made to solve the above problems, the object of which is to measure the dimensions of the workpiece, without changing the mounting state of the tool and the workpiece during machining, numerical control machine tool that can be processed by correcting the machining dimensions To provide.

Another object of the present invention is to provide a machining dimension measuring apparatus capable of measuring the dimensions of a workpiece.

In order to achieve the above object, according to the first concept of the present invention, the machine tool shown in FIG. 1 is provided, and the machine tool which processes the workpiece by the processing means 9 includes the machine tool 2 with respect to the workpiece. The numerical control device 1 for controlling the relative movement of the machining means 9 mounted on the main shaft of the controller, and the contact detector 4 for detecting the position of the workpiece and outputting a position signal indicating the detected position. And a machining dimension measuring device 3 mounted near the spindle 12 to measure the machining dimension of the workpiece, and the contact detector 4 after machining the workpiece by the machining means 9. First measuring means (5) for storing the first position signal in contact with the machining surface and second measuring means (6) for storing the second position signal in contact with the machining reference surface (4). And the first and second position signals obtained by the first and second measuring means 5 and 6, respectively. Therefore, the machining error calculating means 7 which calculates a machining error from the difference between the machining surface and the reference plane of the workpiece after machining and outputs an error signal, and the tool correction error correction means 8 which generates an error correction signal in accordance with the error signal. The numerical control device 1 is configured to control a relative movement of the processing means 9 with respect to the workpiece in accordance with the error correction signal to process the workpiece having almost no error.

According to a second aspect of the present invention, there is provided a machining dimension measuring apparatus shown in FIGS. 3A and 3B, and a machining dimension for use in a machine tool for processing a workpiece by machining means mounted on the headstock 12. The measuring device 3 is supported so as to be able to swing on one side of the headstock 12, and detects a bell crank 23 having a first arm 23A and a second arm 23B, and a position thereof. It is disposed between the contact detector 4 fixed to the end of the first arm 23A for outputting a position signal indicating the detected position, and between the second arm 23B and the shaft 27. And the contact detector 4 between the first position, which is a measurement position at which the contact detector 4 is in contact with the workpiece, and the second position, which is a storage position away from the workpiece, by swinging the belt rank 23. It is characterized by consisting of an actuator 26 for moving the).

A first embodiment of the present invention will be described with reference to FIGS. 3A, 3B and 6. 3A and 3B are front views showing the grinding wheel to which the present invention is applied.

The headstock 12 is installed in the fixed column 11 so as to be movable in the vertical direction. In addition, the table 13 is movable in left, right, and front and rear directions. The headstock 12 and the table 13 are driven by a transfer motor (not shown), and the position thereof is controlled by the NC device 1. The jig 14 is fixed on the table 13, and the workpiece | work 15 which consists of ceramic materials, for example, is remounted on the jig 14. The grinding tool 17 is attached to the spindle 16 provided so as to rotate on the spindle 12, and the workpiece 15 is ground.

The machining dimension measuring apparatus 3 is provided on the side surface of the main shaft 12. That is, the box bracket 21 is fixed to the lower side of the main shaft 12, and the bell crank 23 is supported so that the bell crank 23 can be rocked by the roll bearing 22 provided in the bracket 21. As shown in FIG. The contact detector 4 is fixed to the tip of one arm (long arm) or 23A, which is the first arm of the Velk bank 23. As this contact detector 4, a high precision switch etc. which are especially excellent in repeatability are used. The bracket 25 is fixed to the upper side of the headstock 12, and the air pressure is between the bracket 25 and the other arm (short arm), 23B, which is the second arm of the bell crank 23. The cylinder 26 is connected. The rear end of the head portion of the pneumatic cylinder 26 is pivotally connected to the bracket 25 by the shaft 27, while the connecting member 29 is fixed to the front end of the piston rod 28, and the connecting member ( It is connected to the short arm 23B of the bulk crank 23 so that the shaft 30 provided in 29 can oscillate. The pneumatic cylinder 26 serves as an actuator for swinging the bell crank 23.

The stopper 31 protrudes and is provided in the vicinity of the support part of the long arm 23A of the bell crank 23. As shown in FIG. 3B, the stopper 31 abuts against the side surface of the main shaft 12 when the piston rod 28 of the pneumatic cylinder 26 is extended to adjust the swing position of the bell crank 23. Regulate. The swinging position where the pneumatic cylinder 26 is extended and the stopper 31 abuts against the spindle 12 is a measuring position where the contact detector 4 can contact the workpiece 15. On the other hand, the pneumatic cylinder 26 is retracted so that the swinging position shown in FIG. 3A in which the long arm 23A of the bell crank 23 is directed to the side of the main shaft 12 becomes the storage position.

At the measurement position, the bell crank 23 is fixed in a state where the stopper 31 abuts against the spindle 12 by the force applied by the pneumatic cylinder 26. Therefore, even if the rotation center axis of the roll bearing 22 flows by several microns, it is reliably fixed in the state pressed by the stopper 31, and the position of the contact detector 4 does not flow. Thus, the machining dimension measuring apparatus 3 according to the present embodiment has the advantage that the movement of the contact detector 4 and the fixing to the measurement position can be simultaneously performed as one pneumatic cylinder 26 functioning as an actuator.

In this embodiment, the upper surface 15A of the work piece 15 is ground to finish the height dimension to the target dimension. Machining, measuring, and correction processing therefor are carried out continuously. They are realized as the processing of the computer in the NC apparatus 1. 6 is a flowchart showing processing of the computer.

When step 100 is started, machining (grinding) of the workpiece 15 is first performed in accordance with the NC machining program given in step 101. At this time, the pneumatic cylinder 26 is retracted so that the contact detector 4 is placed in a storage position. When the machining is terminated, the program proceeds to Step 102 where the main shaft 12 is raised, and then the pneumatic cylinder 26 is extended to set the bell crank 23 to the measurement position. In step 103, the headstock 12 and the table 13 are moved, and the touch detector 4 contacts the machining surface 15A of the workpiece 15 and lowers the headstock 12 until a contact signal is input. Let's do it. In step 104, the first position of the headstock 12 at the time of detecting a contact is stored as positional information H ₁ . The processing in steps 103 and 104 constitutes the first measuring means 5.

In step 105, the headstock 12 is once lifted up so that the contact detector 4 is separated from the work piece 15, and the table 13 is moved to the contact reference surface 4A on the machining reference surface 14A of the jig 14. Lower the main shaft 12 to contact the. In step 106, the second position of the headstock 12 at the moment of detecting the contact is stored as the positional information H ₂ . The processing in steps 105 and 106 constitutes the second measuring means 6.

Next, in step 107, the headstock 12 is raised, and the pneumatic cylinder 26 is retracted to set the bell crank 23 to the storage position.

In step 108, according to the position information H _l, H ₂ represents the spindle units in place of the first and second calculates the machining dimension of the workpiece (15), and calculating a machining error between the target dimensions. If the calculated machining error is within the predetermined allowable value, the process proceeds from step 109 to step 11, and the program ends. If the machining error is equal to or greater than the predetermined allowable value, the flow proceeds from step 109 to step 110. In step 110, the tool correction value set and stored in the NC device 1 is corrected by the error in order to correct the machining error. In step 111, the workpiece 15 is reworked using the corrected tool correction value, and the series of processing ends in step 112. FIG.

As described above, in this machine tool, after machining the workpiece 15, the workpiece 15 and the grinding tool 17 are not separated from the machine tool, but the machining dimensions are measured in the same state. The correction value is corrected and reworked immediately. Therefore, the tool correction value after correction includes all the various error factors depending on the state of the machine such as thermal displacement and tool wear at that time, so that high precision machining is possible. Moreover, since a series of these processes are performed automatically, the time required for this is small and high processing efficiency can be ensured.

This embodiment uses a high-precision switch for the contact detector 4, and mechanically detects the position of the machining surface 15A of the workpiece 15, so that it is easily applied to the workpiece 15 made of nonferrous materials such as ceramics. can do. Moreover, there exists an advantage that it can provide in low cost.

In the above embodiment, the case where the height dimension of the work piece 15 is corrected has been described as an example, but a plurality of contact detectors for detecting contact from each direction are provided at the tip of the long arm 23A of the bell crank 23. It is also possible to detect and correct the width dimension of the work piece 15.

As described above, according to the first embodiment, there is an excellent effect that high-precision machining with various error factors such as thermal displacement and tool wear can be corrected.

In addition, since the processing dimension measuring apparatus of the present invention facilitates the movement and fixation of the contact detector by one actuator, the structure is simple and can be provided at low cost, and it is very easy to mount on an existing tool machine. It works. Therefore, the tool machine of the present invention can be converted as a simple modification of the existing tool machine.

Next, a second embodiment of the present invention will be described with reference to FIGS. 4A, 4B, 5 and 7. 4A and 4B are front views showing a second embodiment of the present invention, wherein reference numerals as shown in FIGS. 3A and 3B denote the same parts as shown here. Therefore, description thereof is omitted.

On the processing table 13, a dressing device 50 and a reference block 55 are provided. The dressing apparatus 50 includes a truing or dressing grindstone, 51, and is rotated about a vertical axis by a motor (not shown). The upper surface of the dressing grindstone 51 is the grinding surface 51A, and the lower surface 17A of the grinding tool 17 for processing attached to the main shaft 16 is trued or dressed. The reference block 55 is to give a surface to be the reference of the height position, the upper surface is a reference surface 55A. The stopper 31 abuts against the side surface of the headstock 12 when the piston rod 28 of the pneumatic cylinder 26 is extended, and the contact detector 4 contacts the grinding surface 51A of the dressing grind 51 or the reference. The measuring position is brought into contact with the reference surface 55A of the block 55. On the other hand, the piston rod 28 of the pneumatic cylinder 26 is retracted so that the swinging position shown in Fig. 4A in which the long arm 23A of the bell crank 23 faces the side of the main shaft 12 becomes the storage position.

5 is a diagram showing the positional relationship between various members during dressing.

Z-axis origin size #A from the machine origin 60 to the upper surface of the machining table 13 is a machine-specific value and is known in advance. The spindle 12 is lowered from the machine origin 60, and the grinding tool 17 mounted on the spindle 16 is polished together with the dressing grinding wheel 51 to perform truing or dressing. At this time, the final lowered position of the headstock 12, that is, the end position H ₀ , which determines the cutting amount of the dressing can be known by the feedback data or the feed command value inside the NC apparatus 1. This end point position H ₀ represents the final position where the headstock 12 is moved along the cutting depth through the dressing.

After the dressing is finished, the position H ₁ of the grinding surface 51A of the dressing grindstone 51 and the position H ₂ of the reference surface 55A of the reference block 55 are measured using the measuring device 3. The origin of these two measurement positions H ₁ and H ₂ is different from the machine origin 60, but does not matter. The height dimension #E of the reference block 55 is a known value.

Tool length T _L and dressing grind of the grinding tool 17 after dressing using the end point position H ₀ , the grinding surface position H ₁ , the reference surface position H ₂ , the reference block height dimension #E and the Z axis origin dimension #A. The decrease A ₁ of (51) can be calculated.

Tool length T _L is calculated by the following equation.

T _L = # A- {H ₀ + # E + (H ₂ -H ₁ )}. … … … … … … … … … … … … … (One)

The reduction amount A ₁ of the dressing grindstone 51 is represented by the following formula.

A ₁ = # C _{1 -L} -{# E + (H ₂ -H _l )}. … … … … … … … … … … … … … … (2)

Here, #C _1-L is the height dimension of the dressing grindstone 51 before dressing execution.

Therefore, the dressing height dimension #C is updated as follows.

# C = # C _{1 -L} -A ₁ . … … … … … … … … … … … … … … … … … … … … (3)

In addition, the reduction amount A ₂ of the grinding tool 17 by dressing can also be calculated | required by the following formula.

A ₂ = [total depth of cut] -A ₁ ... … … … … … … … … … … … … … … … … … … (4)

Here, the total depth of cut can be known from the command value of the dressing program inside the NC apparatus 1.

Therefore, the Z-axis coordinate of the dressing start position at the next dressing is

_Starting point = H ₀₊ A ₂ . … … … … … … … … … … … … … … … … … … … … (5)

Can be updated with

By modifying the dressing program at the dressing start point updated as described above, the cutting amount of the next dressing can be maintained at an appropriate predetermined value.

The truing or dressing operation, the measuring operation, various calculations, and the modification of the dressing program described above are realized as the processing of the computer in the NC apparatus 1.

7 is a flowchart showing the processing of the computer. When step 200 is initiated, the grinding tool 17 is moved to the truing or dressing macro point according to the truing or dressing program first given in step 201. In step 202, the grinding tool 17 and the dressing grindstone 51 are rotated and polished together, so that truing or dressing is performed. At this time, the pneumatic cylinder 26 is retracted so that the contact detector 4 is placed in a storage position. When truing or dressing ends, the program proceeds to step 203, and the final position of the headstock 12 is stored as the end position H ₀ . Step 203 configures the first measuring means 42.

In step 204, the headstock 12 is raised, and then the piston rod 28 of the pneumatic cylinder 26 is extended to set the bell crank 23 to the measurement position. In step 205, the headstock 12 and the machining table 13 are moved so that the contact detector 4 contacts 51A of the grinding surface of the dressing grindstone 51, and the headstock 12 until the connection signal is input. Down). In step 206, the position H ₁ of the headstock 12 at the time when a contact is detected is stored. The processing in step 205 and step 206 constitutes second measuring means 43.

In step 207, the headstock 12 is once raised to move the contact detector 4 away from the dressing grind 51, and the machining table 13 is moved to contact the upper surface 55A of the reference block 55. The headstock 12 is lowered to contact the detector 4. In step 208, the position H ₂ of the headstock 12 at the moment of detecting the contact is stored. The processing in steps 0 207 and 208 constitutes third measuring means 14.

In step 209, the main shaft 12 is raised to retract the pneumatic cylinder 26 to set the bell crank 23 to the storage position.

In step 210, the position information memorized and measured in steps 203, 206, and 208, that is, the end point positions H ₀ , the first and second positions H _l , H _2, and the Z-axis origin of the known main axis 12 According to the dimension #A and the height dimension #E of the reference block 55, the tool length T _L is calculated according to the above formula (1), and set to the empty correction area of the numerical control device 41. Step 210 configures the tool length calculating means 45 and the tool length setting means 46.

In step 211, the amount of reduction, dressing the grinding wheel 51 according to the position information H _l, H ₂ and the dimensions of the base #E, #C _1-L and the depth of cut command program at the time of dressing stored in step 206 and 208 A The reduction amount A ₂ of ₁ and the grinding tool 17 is computed according to said Formula (2), (4), respectively. The process of step 211 constitutes a reduction amount ejection means 47.

In step 212, the new dressing wheel height dimension #C is calculated and updated according to the above Equation (3), and the position of the next dressing start point is calculated according to the above Equation (5). Or modify the program data for dressing. The process of step 212 constitutes the dressing data correction means 48. As described above, the series of programs for truing or dressing is finished in step 213, and the workpiece is ground using the tool length T _L set this time. In the subsequent grinding process, the workpiece can be ground within the allowable range while measuring the amount of grinding according to the first embodiment.

As described above, in the grinding machine according to the second embodiment, the grinding tool 17 is not separated from the spindle 16 after the truing or dressing of the processing grinding tool 17 is finished, and the dressing grindstone remains as it is. By measuring the grinding surface 51A of the 51 and the reference surface 55A of the reference block 55, high-precision air length is set, and the program data for truing or dressing for truing or dressing again Is correcting. Moreover, since these series of processes are performed automatically, the time required for the process is small, the memory efficiency is improved, and the skill of the operator is also unnecessary.

Since the grinding machine according to the second embodiment is configured as described above, the tool length after truing or dressing can be measured automatically and the tool length can be set with high precision without separating the grinding tool from the main shaft. It is effective. Therefore, the precision of grinding processing is improved and work efficiency is improved. In addition, in the second aspect of the present embodiment, the program for truing or dressing can be automatically corrected in accordance with the reduced amount of grindstone. Therefore, it becomes possible to automatically repeat the processing cycle which consists of a process from dressing to actual grinding, and the processing efficiency improves.

Claims (9)

A numerical controller for controlling the relative movement of the machining means mounted on the main shaft of the machine tool with respect to the workpiece, and a contact detector for detecting the position of the workpiece and outputting a position signal representing the detected position, A first dimension measurement device which is mounted in the vicinity of the main shaft and measures a machining dimension of the workpiece, and a first position signal in which the contact detector contacts the machining surface of the workpiece after machining of the workpiece by machining means; Processing according to the first and second position signals obtained by the means, second measurement means for storing the second position signal in which the contact detector contacts the machining reference plane, and the first and second measurement means. Machining error calculating means for calculating a machining error from the difference between the machined surface and the reference plane of the subsequent workpiece and outputting an error signal, and generating an error correction signal in accordance with the error signal. And a tool correction value error correcting means, wherein the numerical control device controls the relative movement of the processing means with respect to the workpiece to process the workpiece with little error. The machine tool according to claim 1, wherein the machining dimension measuring device is movably mounted on the main shaft, and moves to the workpiece side to detect the position of the machining surface. The machine tool according to claim 2, wherein the machining dimension measuring device moves to a machining reference plane side. 2. The cutting machine according to claim 1, wherein the processing dimension measuring device is supported so as to be able to swing on one side of the main shaft, and has a bell crank having a first arm and a second arm, and a position signal indicating a position detected by detecting the position. A first contact detector fixed to an end of the first arm to be output and disposed between the second arm and the shaft, the first position being a measurement position where the contact detector can contact the workpiece by oscillating the bell grank. And an actuator for moving said contact detector between a position and a second position, a storage position away from the workpiece. 5. The processing apparatus according to claim 4, wherein the processing dimension measuring device also has a stopper attached to a bell crank, the stopper contacting one side of the main side when the contact detector is moved to a first position to stop the swing of the pulling bell grank. Machine tool which is regulated. 6. The actuator according to claim 5, wherein the actuator applies a force to the second arm to move the contact detector from a second position to a first position, and the stopper stops the swing of the crank against the applied force. Machine tool which is regulated. A machining dimension measuring device for use in a machine tool for processing a workpiece by a machining means mounted on the spindle, wherein the bell crank is supported to swing on one side of the spindle and has a first arm and a second arm; A contact detector fixed to an end of the first arm that detects the position and outputs a position signal indicating the detected position, and is disposed between the second arm and the shaft, and swings the bell crank to And a actuator for moving the contact detector between a first position, which is a measurement position at which the contact detector is in contact with the workpiece, and a second position, which is a storage position away from the workpiece. 8. A stopper according to claim 7, further comprising a stopper attached to said bell crank, said stopper contacting one side of said main shaft when said contact detector is moved to a first position to regulate the fluctuation of said bell crank. Processing dimension measuring device. 9. The actuator according to claim 8, wherein the actuator applies a force to the second arm to move the contact detector from a second position to a first position, and the stopper stops the swing of the crank against the applied force. Process dimension measuring device, characterized in that regulated.

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